• Serialization:
  • The process of creating a "frozen" representation of a "live" (i.e., in-memory) object
• "Naive" Approaches:
  • Agnore the complications introduced by references

• Possible Formats:
  • XML
  • JSON
• What's Needed:
  • Method(s) to create a String representation in the chosen format
  • Factory method(s) to create an object from a String representation in the chosen format

javaexamples/jaxp/Person.java

        import java.io.*;
import org.w3c.dom.*;

/**
 * An encapsulation of a Person.
 * 
 * This is an example of "naive" serialization.
 * 
 * @author  Prof. David Bernstein, James Madison University
 * @version 1.0XML
 */
public class Person
{
    private Address       address;
    private int           age;
    private PhoneNumber[] phoneNumbers;
    private String        firstName, lastName;
    
    /**
     * Construct an empty Person object.
     */
    private Person()
    {
    }

    /**
     * Populate the attributes of this Person object from
     * an XML representation.
     * 
     * @param source  The XML representation
     */
    public void fromXML(Element source)
    {
        NodeList nodes;
        
        firstName  = source.getAttribute("firstName");
        lastName   = source.getAttribute("lastName");
        age        = Integer.parseInt(source.getAttribute("age"));
        
        nodes = source.getElementsByTagName("Address");
        address = Address.parseAddress((Element)nodes.item(0));
        
        nodes = source.getElementsByTagName("PhoneNumber");
        phoneNumbers = new PhoneNumber[nodes.getLength()];
        for (int i=0; i<nodes.getLength(); i++)
        {
            phoneNumbers[i] = PhoneNumber.parsePhoneNumber((Element)nodes.item(i));
        }
    }
    
    /**
     * Construct a Person object from an XML representation.
     * 
     * @param source  The XML representation
     * @return        The Person object
     */
    public static Person parsePerson(Element source)
    {
        Person result = new Person();
        result.fromXML(source);
        return result;
    }

    /**
     * Create an XML representation of this Person.
     * 
     * @return The XML representation
     */
    public String toXML()
    {
        String result = String.format("<Person firstName=\"%s\" lastName=\"%s\" age=\"%s\" >",
                                      firstName, lastName, age);
        
        result += "\n" + address.toXML();
        for (int i=0; i<phoneNumbers.length; i++)
        {
            result += "\n" + phoneNumbers[i].toXML();
        }
        
        result += "\n" + "</Person>";
        
        return result;
    }

}
        

javaexamples/jaxp/Address.java

        import java.io.*;
import org.w3c.dom.*;


/**
 * An encapsulation of an Address.
 * 
 * This is an example of "naive" serialization.
 * 
 * @author  Prof. David Bernstein, James Madison University
 * @version 1.0
 */
public class Address
{
    private int    postalCode;
    private String city, state, streetAddress;

    /**
     * Construct an empty Person object.
     */
    private Address()
    {
    }

    /**
     * Populate the attributes of this Address object from
     * an XML representation.
     * 
     * @param source  The XML representation
     */
    public void fromXML(Element source)
    {
        streetAddress  = source.getAttribute("streetAddress");
        city       = source.getAttribute("city");
        state      = source.getAttribute("state");
        postalCode = Integer.parseInt(source.getAttribute("postalCode"));
    }
    
    /**
     * Construct an Address object from an XML representation.
     * 
     * @param source  The XML representation
     * @return        The Address object
     */
    public static Address parseAddress(Element source)
    {
        Address result = new Address();
        result.fromXML(source);
        return result;
    }

    /**
     * Create an XML representation of this Address.
     * 
     * @return The XML representation
     */
    public String toXML()
    {
        return String.format("<Address streetAddress=\"%s\" city=\"%s\" state=\"%s\" postalCode=\"%s\" />",
                streetAddress, city, state, postalCode);
    }
}
        

javaexamples/jaxp/PhoneNumber.java

        import java.io.*;
import org.w3c.dom.*;

/**
 * An encapsulation of a PhoneNumber.
 * 
 * This is an example of "naive" serialization.
 * 
 * @author  Prof. David Bernstein, James Madison University
 * @version 1.0
 */
public class PhoneNumber
{
    private String number, type;
    
    /**
     * Construct an empty PhoneNumber object.
     */
   private PhoneNumber()
    {
    }

   /**
    * Populate the attributes of this PhoneNumber object from
    * an XML representation.
    * 
    * @param source  The XML representation
    */
   public void fromXML(Element source)
   {
       number  = source.getAttribute("number");
       type    = source.getAttribute("type");
   }
   
   /**
    * Construct a PhoneNumber object from an XML representation.
    * 
    * @param source  The XML representation
    * @return        The Person object
    */
   public static PhoneNumber parsePhoneNumber(Element source)
   {
       PhoneNumber result = new PhoneNumber();
       result.fromXML(source);
       return result;
   }
    /**
     * Create an XML representation of this PhoneNumber.
     * 
     * @return The XML representation
     */
    public String toXML()
    {
        return String.format("<PhoneNumber type=\"%s\" number=\"%s\" />",
                type, number);
    }
}
        

javaexamples/jaxp/PersonDriver.java

        import java.io.*;
import org.w3c.dom.*;
import javax.xml.parsers.*;

/**
 * A driver for an example that illustrates the use of XML
 * for "naive" serialization.
 *
 * @author  Prof. David Bernstein, Jmes Madison University
 * @version 1.0
 */ 
public class PersonDriver
{
    /**
     * The entry point of the application.
     *
     * @args  The command line arguments (ignored)
     */
    public static void main(String[] args) throws Exception
    {
        File file = new File("person.xml");
        
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder        builder = factory.newDocumentBuilder();
        Document               document = builder.parse(file);
        Element                root = document.getDocumentElement();

        Person q = Person.parsePerson(root);

        System.out.println(q.toXML());
    }
}
        

javaexamples/jsonp/Person.java

        import java.io.*;
import javax.json.*;
import javax.json.stream.*;

/**
 * An encapsulation of a Person.
 * 
 * This is an example of "naive" serialization.
 * 
 * @author  Prof. David Bernstein, James Madison University
 * @version 1.0JSON
 */
public class Person
{
    private Address       address;
    private int           age;
    private PhoneNumber[] phoneNumbers;
    private String        firstName, lastName;
    
    /**
     * Construct an empty Person object.
     */
    private Person()
    {
    }

    /**
     * Populate the attributes of this Person object from
     * a JSON representation.
     * 
     * @param source  The JSON representation
     */
    public void fromJSON(JsonObject source)
    {
        firstName = source.getString("firstName");
        lastName  = source.getString("lastName");
        age       = source.getInt("age");
        
        address = Address.parseAddress(source.getJsonObject("address"));
        
        JsonArray pns = source.getJsonArray("phoneNumbers");
        phoneNumbers = new PhoneNumber[pns.size()];
        for (int i=0; i<phoneNumbers.length; i++)
        {
            JsonObject pn = pns.getJsonObject(i);
            phoneNumbers[i] = PhoneNumber.parsePhoneNumber(pn);
        }
    }
    
    /**
     * Construct a Person object from a JSON representation.
     * 
     * @param source  The JSON representation
     * @return        The Person object
     */
    public static Person parsePerson(JsonObject source)
    {
        Person result = new Person();
        result.fromJSON(source);
        return result;
    }

    /**
     * Create a JSON representation of this Person.
     * 
     * @return  A String containing the JSON representation
     */
    public String toJSON()
    {
        StringWriter out = new StringWriter();
        JsonGenerator g = Json.createGenerator(out); 
        toJSON(g, null);
        g.close();
        
        return out.toString();
    }
    
    /**
     * Create a JSON representation of this Person using the
     * given JsonGenerator.
     * 
     * @param g     The JsonGenerator to use
     * @param name  The name for the JsonObject (or null for none)
     */
    public void toJSON(JsonGenerator g, String name)
    {
        if (name == null) g.writeStartObject();
        else              g.writeStartObject(name);
          g.write("firstName", firstName);
          g.write("lastName", lastName);
          g.write("age", 25);
          address.toJSON(g, "address");
          g.writeStartArray("phoneNumbers");
            for (int i=0; i<phoneNumbers.length; i++)
            {
                phoneNumbers[i].toJSON(g, null);
            }
          g.writeEnd();
        g.writeEnd();
    }
}
        

javaexamples/jsonp/Address.java

        import java.io.*;
import javax.json.*;
import javax.json.stream.*;


/**
 * An encapsulation of an Address.
 * 
 * This is an example of "naive" serialization.
 * 
 * @author  Prof. David Bernstein, James Madison University
 * @version 1.0JSON
 */
public class Address
{
    private int    postalCode;
    private String city, state, streetAddress;

    /**
     * Construct an empty Person object.
     */
    private Address()
    {
    }
    
    /**
     * Populate the attributes of this Address object from
     * a JSON representation.
     * 
     * @param source  The JSON representation
     */
    public void fromJSON(JsonObject source)
    {
        streetAddress = source.getString("streetAddress");
        city = source.getString("city");
        state = source.getString("state");
        postalCode = source.getInt("postalCode");
    }

    /**
     * Construct an Address object from a JSON representation.
     * 
     * @param source  The JSON representation
     * @return        The Address object
     */
    public static Address parseAddress(JsonObject source)
    {
        Address result = new Address();
        result.fromJSON(source);
        return result;
    }

    /**
     * Create a JSON representation of this Address.
     * 
     * @return  A String containing the JSON representation
     */
    public String toJSON()
    {
        StringWriter out = new StringWriter();
        JsonGenerator g = Json.createGenerator(out); 
        toJSON(g, null);
        g.close();

        return out.toString();
    }

    /**
     * Create a JSON representation of this Person using the
     * given JsonGenerator.
     * 
     * @param g     The JsonGenerator to use
     * @param name  The name for the JsonObject (or null for none)
     */
    public void toJSON(JsonGenerator g, String name)
    {
        if (name == null) g.writeStartObject();
        else              g.writeStartObject(name);
        g.write("streetAddress", streetAddress);
        g.write("city", city);
        g.write("state", state);
        g.write("postalCode", postalCode);
        g.writeEnd();
    }
}
        

javaexamples/jsonp/PhoneNumber.java

        import java.io.*;
import javax.json.*;
import javax.json.stream.*;

/**
 * An encapsulation of a PhoneNumber.
 * 
 * This is an example of "naive" serialization.
 * 
 * @author  Prof. David Bernstein, James Madison University
 * @version 1.0JSON
 */
public class PhoneNumber
{
    private String number, type;
    
    /**
     * Construct an empty PhoneNumber object.
     */
    private PhoneNumber()
    {
    }
   
   /**
    * Populate the attributes of this PhoneNumber object from
    * a JSON representation.
    * 
    * @param source  The JSON representation
    */
    public void fromJSON(JsonObject source)
    {
        type = source.getString("type");
        number = source.getString("number");
    }

    /**
     * Construct a PhoneNumber object from a JSON representation.
     * 
     * @param source  The JSON representation
     * @return        The Person object
     */
    public static PhoneNumber parsePhoneNumber(JsonObject source)
    {
        PhoneNumber result = new PhoneNumber();
        result.fromJSON(source);
        return result;
    }
 
    /**
     * Create a JSON representation of this PhoneNumber.
     * 
     * @return  A String containing the JSON representation
     */
    public String toJSON()
    {
        StringWriter out = new StringWriter();
        JsonGenerator g = Json.createGenerator(out); 
        toJSON(g, null);
        g.close();
        
        return out.toString();
    }

    /**
     * Create a JSON representation of this PhoneNumber using the
     * given JsonGenerator.
     * 
     * @param g     The JsonGenerator to use
     * @param name  The name for the JsonObject (or null for none)
     */
    public void toJSON(JsonGenerator g, String name)
    {
        if (name == null) g.writeStartObject();
        else              g.writeStartObject(name);
          g.write("type", type);
          g.write("number", number);
        g.writeEnd();
    }
}
        

javaexamples/jsonp/PersonDriver.java

        import java.io.*;
import javax.json.*;

/**
 * An example of "naive" serialization using JSON.
 *
 * @author  Prof. David Bernstein, James Madison University
 * @version 1.0
 */
public class PersonDriver
{
    /**
     * The entry point of the application.
     *
     * @param args  The command line arguments (ignored)
     */
    public static void main(String[] args) throws Exception
    {
        File file = new File("person.json");
        
        BufferedReader in = new BufferedReader(new FileReader(file));
        JsonReader reader = Json.createReader(in);
        JsonObject person = reader.readObject();
        
        Person p = Person.parsePerson(person);
        System.out.println(p.toJSON());
    }
}
        

• Possible Interfaces:
  • XMLable
  • JSONable
• What They Add:
  • The notion that something can be converted to/from XML and/or JSON